Often, it is desirable to inject an image or visual indicator into an image as viewed through a rifle sight, telescope, video camera or other viewing optical system. Such an injected image may supplement an image of a scene being viewed through the viewing optical system, for example by highlighting a portion of the image of the scene or by overlaying the image of the scene with a visual image of the scene in a non-visible portion of the electromagnetic spectrum. A visual indicator other than an image may be injected to provide a user of the viewing optical system with an indicator that may be viewed within the image of the scene. Such an indicator may provide an alert, warning, failure or other sort of indication.
Typically, image injectors are undesirably large and/or heavy. Known image injectors may also be fragile or subject to degraded performance in inclement operating conditions.